This apparatus is an improvement upon lifting devices such as supporting, gripping and pressure tongs used in manufacturing, demolition and material handling. Generally, lifting devices of these types are designed for a particular function or designed to lift a particular size and shape. The gripper described here is designed to incorporate the function of gripping, supporting, and pressure tongs in one device and may lift and support objects of varying size and shape. Shapes that may be lifted by the grippers include bars, pipes, tubes, T-shapes, angles, I-beams, and plates.
Supporting tongs are known and used to support objects of a particular configuration. The objects lifted and supported by supporting tongs are required to have clearance at the base of the object to allow space for the feet of the tong or gripper to contact the bottom of the object. Supporting tongs have opposing arms that are not intended to close completely together because they are designed to lift objects of a known and constant size. The gripper described here uses fingers with inclined tips that taper and act as a wedge to facilitate lifting objects directly off the floor and into the center of the device. The gripper is designed to allow complete closure of the opposing finger sections and may slightly over close allowing flexibility to lift variously sized and shaped objects. The wedge shape and inclined fingers allow the gripper to pick up objects that do not have the clearance required for use of supporting tongs.
Pressure tongs grip the vertical sides of an object, such as boxes, ingots or other right-sided objects, and apply friction to allow lifting of the object. Once objects have been lifted by the fingers of the gripper described here and the object is in or near the center of the gripper, a moveable arm squeezes the vertical sides together applying the friction required to lift the object similar to the only function of pressure tongs.
Gripping tongs, used to lift round or cylindrical objects, grip the object around the circumference with the tongs extending below the center of the object with the tongs generally in continuous contact with the rounded surface of the object. Like supporting tongs, gripping tongs have opposing arms that are not intended to close completely together. In the case of gripping tongs, they are designed to lift objects of a size range varying by about 25% and the tongs will extend just below the center of the of the object and are not designed to completely envelop the cylindrical or round object. If round or cylindrical items are to be lifted, the gripper described here supports the item below the center of the item in cradle-like hold. The gripper described here may not continuously contact the surface of round or cylindrical items, but will completely envelop the object.
The gripper provides an attachment point for a crane hook and is used for lifting, grasping, and/or supporting various structures and structural shapes in random positions. The gripping tool has two opposing finger sections. One finger section is stationary and has four individual fingers, the other finger section is moveable and has three individual fingers. There is space between the fingers of each section to allow the opposing sections to interlock. The opposing finger sections may close together allowing the inclined, tapered tips to extend beyond the plane defined by the opposing finger section's engagement surface. Thus, the interlocking fingers enable the gripper to lift and support objects of varying sizes. The interlocking fingers are more likely to bend, rather that crush or shear the lifted object if the gripper is closed too tightly. The ability to bend rather than crush or shear the object being lifted serves to decrease the amount of material that may become permanently damaged, especially thin wall tubing, if the gripper is inadvertently over-closed. Materials that become bent are more easily returned to their intended shape as compared to materials that become crushed or sheared.
Gripping tools currently known in the art to have interlocking or inter-fitting components do not allow the opposing components to close beyond the boundary defined by the opposing section because one jaw will confront the engagement surface of the opposing jaw. Examples of these types of tools are in U.S. Pat. Nos. 4,199,972 and 4,283,933 issued to Weiner.
Gripping tools currently known to have one moveable and one stationary arm are used to open and close tightly sealed containers. These tools do not have lifting bails or interlocking fingers that can extend beyond the engagement surface of the opposing arm. An example is in U.S. Pat. No. 3,862,776 issued to Sims and Borello.
The gripper may provide significant cost savings for manufacturing, demolition and material handling operations because this one device can lift and support objects of varying size and shape and thereby may eliminate the need to design supporting, gripping or pressure tongs to perform each particular function. Additional cost savings may result from the gripper's tendency to bend rather than crush or shear objects if the gripper is over-closed around the object.